Are ideas just so bad, or is validation too strict? I will not promote

Ideas are great, but they don't always work in the real world. So far, none of the ideas I've looked at seem to pass validation. They all end up somewhere in the "medium confidence" range. When I read the reasoning, I agree. The risks make sense, the business model has issues, and the demand is just not there. It's a weird feeling. The idea sounds great in my head. You talk to someone about it, they agree, and you start dancing. Then you validate it and things go sour. What ever happened to that gut feeling?! Is it just overconfidence? Sometimes it makes me wonder why I should even start if the idea doesn't look like it has a higher than average chance of working out. Is it really that difficult to have a "good idea"? Then I see Kevin down the road, 19 years old, with his stupid little site that he "made" last night, already getting offers and 1216 users. How do ideas that were "meh" turn into gold? What do you think? Have you moved forward with building or starting a business "against the odds", without strong validation, and actually made it work?